A bus bar connector assembly may comprise a frame, for example an electrical module in which a bus bar is fixedly mounted, a drawer mounted power supply unit, being slidable in the frame towards and away from the bus bar, and having means for connecting circuitry in the module with the bus bar, for the supply of power to the bus bar. The electrical circuitry of such a module may be constituted, for example, by printed circuit boards mounted in superposition in the module. Conventionally, an electrical lead extending from the module has been secured to the bus bar by means of bolts, to connect the circuitry to its bus bar. The disconnection of the module from the bus bar, in order to allow repair work to be carried out on the module, and subsequent reconnection of the module to the bus bar were, therefore, time consuming. Furthermore, the threaded connection between the lead and the bus bar was subjected to temperature cycling owing to the heat generated by the module, thus causing the bolt to loosen as a result of differential expansion between the metal of the bolt and that of the bus bar, thereby necessitating periodical readjustment of the bolt.